Abstract
Oxidative stress derived from reactive oxygen species and/or heavy metal ions is believed to cause random damage to components in a living body, as well as aging and/or various disorders. A variety of systems that protect the living body from oxidative stress-induced damage are known; the present author elucidated three new defense systems against oxidative stress. Firstly, although it has been thought that lipid peroxidation in the living body promotes oxidative stress and increases the degree of oxidative damage, it was found that lipid peroxidation attenuated the DNA damage induced by such stress. This was determined by careful estimation of in situ lipid peroxidation. Secondly, red blood cells suffered from oxidative stress during their circulation, and membrane band 3 became aggregated and clustered so that anti-band 3 IgG and macrophages attached to it through sialylated poly-N-acctyllactosaminyl (PL) sugar chains. The PL sugar chain attachment to macrophages was stimulated by oxidative stress in the macrophages. Thirdly, the presence of oxidized protein hydrolase (OPH) that preferentially hydrolyzed proteins damaged by oxidative stress was found, and this enzyme may constitute a secondary defense system of the cells against such stress.
